Warfarin is a potent oral anticoagulant drug which is known to inhibit the enzyme vitamin K epoxide reductase. This enzyme has never been purified and its mechanism of action is unknown. The long-term objectives are to understand the mechanism of the enzyme and the mechanism of its inhibition by anticoagulants. Specifically, the enzyme will be purified by raising monoclonal antibodies and isolating the enzyme from beef liver by standard antibody affinity chromatography techniques. The purified enzyme will be characterized and its mechanism of action studied. New inactivators of the enzyme will be synthesized and their mechanism and the mechanism of warfarin will be investigated. The monoclonal antibodies also will be used to clone the gene encoding vitamin K epoxide reductase so that larger quantities of the enzyme can be produced.